DESCRIPTION (Applicant's Abstract): Electromagnetic interstitial applicators can be an effective way of heating cancer. When heated to 42-50oC, the cells loose their ability to divide. In spite of the invasive nature of interstitial therapeutic treatment, these probes offer the opportunity to customize power deposition locally within tumors. The aim of this research is to demonstrate the feasibility of using an inductively coupled resonant microwave interstitial probe to serve two functions simultaneously: (a) as a sensor for monitoring the complex permittivity of the surrounding tissue, and (b) as a hyperthermia applicator for controlled deposition of microwave power patterns. Because tumors are known to contain significantly more bound water than normal tissue, both the real dielectric constant and the conductivity of tumors are also significantly larger. By using the probe to sense the local complex permittivity, it can be properly positioned within the tumor. Further, dynamic changes in the permittivity due to heating can be monitored. This research focuses on the design of microwave frequency probes to optimize their sensitivity to changes in the permittivity and to maximize uniformity of their power deposition patterns. Attention will focus on the manner in which the probe is fed and on achieving uniform power coupling to the tissue along the length of the probe. Power deposition patterns will be experimentally validated using phantom models and innovative field mapping techniques.